A super-high resolution frequency standard measuring approach based on phase coincidence characteristics between signals     

李智奇  周渭  陈发喜  刘晨光 《海洋学报(英文版)》2010,29(9)

A method for super high resolution comparison measurement is proposed in this paper with a comparison between the frequency standards of different nominal frequencies, which is based on phase coincidence detection of the two compared signals. It utilizes the regular phase shift characteristics between the signals. The resolution of the measurement approach can reach 10^-13/s at 5 MHz, and the self-calibration resolution can achieve 10^-14/s in the comparison between 10 MHz and 100 MHz, or even can reach 10^-15/s in the comparison between 10 MHz and 190 MHz. This method implies significant progress in the development of the high precision frequency standard comparison technology.  相似文献   

Methodology for determination of correction factors in direct gamma spectrometric measurement of radionuclides in sediments     

Esra Uyar  Alptu? ?zer Y&#;ksel  Rufiyet G&#;ven  Haluk Y&#;cel 《国际泥沙研究》2017,32(3)

In this study, the practical methodologies are described for the determination of the factors for the self-absorption effect (Fs), spectral interferences (Fcsi), and true coincidence summing effects (Fcoi), which are used in direct gamma-spectrometric measurement of radionuclides such as 210Pb, 238U, 234Th, 226Ra, 214Pb, 228Ac, 208Tl, 214Bi, 137Cs and 40K in samples. To validate the applied methods, certified reference materials (CRMs) of lake and stream sediments were measured with an n-type Germanium (Ge) detector-calibrated using a multinuclide reference source. The highest self-absorption correction factors ranged from Fs = 1.44–2.10 for 46.5 keV peak (210Pb) and Fs = 1.25–1.60 for 63.3 keV peak (234Th) lying in the low energy region of the spectrum. The systematic influence was observed for 186.2 keV (226Ra) peak due to spectral interferences with the 235U contribution. For this peak, Fcsi is changed from 0.921 to 0.955. Additionally, the present study suggests that true coincidence summing (TCS) effects are not dominant, except for 208Tl and 214Bi for which Fcoi ranged from 1.179 to 1.192 an ranged from 1.140 to 1.151, respectively.  相似文献   

综合物探方法在湖北大冶鸡冠咀铜金矿深部及外围找矿中的应用     

邰文星  金尚刚  何彦南  杨梅珍  刘万龙 《地质与勘探》2019,55(4):1010-1025

以鸡冠咀铜金矿床深部及其外围找矿预测为目标,在深入认识鸡冠咀铜金矿床地质特征的基础上,对研究区重力、磁测、电法测量资料进行精细反演,研究含矿地质体与物探异常的对应关系,获取矿区深部和外围物探异常信息。证实研究区岩矿石物性差异明显、与矿有关的地质体与重磁异常具有良好的吻合性,证实研究区内断裂接触带、大理岩俘虏体、隐伏岩体表现出重磁同高、重磁异常梯度带等特征,是寻找深部盲矿体的有利部位。总结了5种地球物理找矿标志,构建了“一个主要目标,两种分析,三种方法,五个找矿标志”的矽卡岩型铜金矿床的地球物理找矿模式,对鸡冠咀矿区深部及外围进行靶区优选,指导鄂东南矿集区矿产勘查工作,具有良好的示范作用。  相似文献   

BOD₅-DO参数反问题偶合模型的研究   总被引：1，自引：0，他引：1  

李兰  李志永  刘金才 《水科学进展》2000,11(3):254-259

根据反问题理论和离散反演算法建立了BOD₅-DO参数反问题偶合模型,并推导出偶合模型的参数解式.对复氧系数、耗氧系数、沉淀-再悬浮系数、光合作用产氧-生物呼吸耗氧系数和自净系数随空间变化规律进行了定量计算,为河流水体自净规律的研究开辟了新途径.  相似文献   

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何志堂  韩宇飞  康胜军  王晓栋  贺小明  李辉  陈永生 《大地测量与地球动力学》2014,34(3):142-145

????A10/028??FG5?????????????α?????????????????????????????????????????????A10/028??FG5????????????????????±5×10^-8 ms^-2????????????????A10/028???????????????????????????????????????????±(2~3)×10^-8 ms^-2??  相似文献